1. Field of the Invention
This invention relates to smoke detection.
2. Description of the Prior Art
Smoke detection systems are well known. One of the most common methods of detecting smoke (and the most frequently used within buildings, such as a person's home) is to have a local detector that physically detects smoke particles in the air. Such smoke detectors are suited to small indoor environments, where the amount of air to be sampled is relatively small. For a large indoor environment, such as a warehouse, multiple such smoke detectors are required to enable detection of smoke in a sufficiently short time. This is a costly solution and is often not easy to deploy. Furthermore, such smoke detectors are not very well suited to detecting smoke in an outdoor environment, such as a park, a forest or a car park. This is due to a variety of reasons, such as: the vast quantity of air present; the lack of a vertical restraint on the movement of the air; the size of the area to be monitored; and potential air flow dynamics that direct smoke away from one or more of the detectors.
Detection of smoke by video/image processing techniques has also been proposed. For example, areas of an image can be compared with known smoke characteristics via pattern matching techniques to detect smoke. For example, smoke plumes may be detected in this manner. Another proposed method of using video based smoke detection is to detect the diffusion of light from light sources and/or bright objects within the video images to identify a pattern consistent with the slow accumulation of smoke.